Tens of thousands of people defied Kremlin efforts to discourage protests on Tuesday as they rallied against Russian President Vladimir Putin.

On Monday Putin launched a pre-emptive strike, as police raided the homes of several prominent protest leaders. They reportedly seized laptops, anti-Kremlin material, and over a million dollars in cash. Those leaders have also been called in for questioning Tuesday, a national holiday in Russia. This will likely prevent them from attending the march and rally.

Authorities said the raids were part of an investigation into violence against riot police during the last protest in May, on the eve of Putin’s inauguration. Analysts, however, say the raids were meant to intimidate the opposition and discourage protests.